The present invention relates generally to an electric compressor and more specifically to an electric compressor that is provided with an injection mechanism.
As a conventional electric compressor, a scroll type compressor such as disclosed in Japanese Patent Application Publication No. H08-303361 is known. The scroll type electric compressor has a power saving mechanism that controls the compression capacity by allowing refrigerant being compressed to flow through a bypass passage toward a low-pressure region of the compressor. The power saving mechanism is provided with a cover plate disposed on the upper surface of a base plate of a fixed scroll member of the compressor. The cover plate has therein a back pressure passage where high pressure refrigerant or low pressure refrigerant is selectively flowed from a unit circuit through a high pressure guide tube and a bypass passage that communicates with the back pressure passage. The bypass passage has a first save-hole, a second save-hole and a return hole. The first save-hole and the second save-hole are formed through the base plate of the fixed scroll member in communication with a compression chamber, and the return hole is also formed through the base plate in communication with a low pressure chamber. The first save-hole, the second save-hole and the return hole are opened to the bypass passage and a first save-valve, a second-save valve and a valve element are provided at the openings of the first save-hole, the second save-hole and the return hole, respectively. The first save-valve, the second-save valve and the valve element are openable/closeable in response to pressure of the refrigerant supplied into the bypass passage.
It is presumed that assembling of the scroll type compressor disclosed in Japanese Patent Application Publication No. H08-303361 is accomplished in the manner described below. Firstly, the cover plate is fixed to the upper surface of the base plate of the fixed scroll member by a bolt. Next, an end cap is mounted so that the cover plate and the base plate of the fixed scroll member are partly covered by the end cap. Then, the high pressure guide pipe, which is connected to a unit circuit, is inserted into a through hole formed through the end cap, and the high pressure guide pipe is connected to the back pressure passage.
However, in order to add a power saving mechanism to the scroll compressor disclosed in the Japanese Patent Publication No. H08-303361, it requires preparing a cover plate having formed therein the bypass passage and the back pressure passage and further having the first saving valve, the second saving valve and the valve element at the openings and forming the first save-hole, the second save-hole and the return hole in the base plate of the fixed scroll member. In addition, a hole needs to be formed through the end cap in which the high pressure pipe is to be inserted. With the opening in the bypass passage aligned properly with the first save-hole, the second save-hole and the return hole, the cover plate is fixed to the upper surface of the base plate of the fixed scroll member by a bolt and the end cap is mounted on the cover plate. Furthermore, the high pressure guide pipe needs to be inserted into the hole formed through the end cap for communication with the back pressure passage. As it is obvious from the above description, adding the power saving mechanism to the scroll type electric compressor requires numerous modifications of parts and increases assembling cost.
The present invention which has been made in light of the problems is directed to providing an electric compressor that can reduce part modification and assembly cost in adding an injection mechanism to the electric compressor.